EFFECT OF EPOXY CONTENT AND NBR MODIFIER ON MECHANICAL PROPERTIES OF COIR FIBRE-POLYESTER NONWOVEN COMPOSITES

Abstract

Coir fibre from coconut husk is an abundant agro-waste with potential as a sustainable composite reinforcement. However, poor interfacial compatibility and high variability limit its applications. This study investigates hybrid coir fibre-polyester nonwoven composites to evaluate the effects of epoxy content and nitrile butadiene rubber (NBR) modification on mechanical properties. The novelty lies in combining NBR-toughened epoxy with layers of coir fibre-polyester needle-punched mats consolidated through hot-press compression moulding. Three layers of coir fibre-polyester mat (50/50%) were produced by needle-punching and impregnated via hand lay-up using 60, 70, 80, 90 vol% epoxy matrixes, with or without 8% NBR. The laminates were consolidated by hot pressing and evaluated through tensile (ASTM D638), flexural (ASTM D790), and Izod Impact (ASTM D256) tests. Fracture mechanisms were analysed using scanning electron microscopy (SEM). B80 achieves the highest tensile (24.93 MPa) and flexural strengths (89.53 MPa). Meanwhile, the addition of 8% NBR reduced tensile and flexural strengths but significantly improved impact strength, C90 (23.46 kJ/m²). Furthermore, C70 and C80 exhibited CoV below 3%, indicating an excellent reproducibility. SEM observations revealed improved fibre-matrix bonding in the Series C,the NBR-modified systems. The findings demonstrate that B80 is more suitable for applications requiring higher stiffness and load-bearing capacity, while C90 is preferable for impact-resistance and energy-absorbing non-structural applications, such as roofing panels, interior building components and protective lightweight panels.